Cam operated fluid pumps

ABSTRACT

This invention relates to a fluid pump comprising a piston which is reciprocable in a cylinder against a biasing force which may be a helical spring. The piston is caused to reciprocate in the cylinder by means of a cam system therein which may be a ball rotated by a helical cam surface on one face of the piston.

mam States Patent Max Edward Grantham Plympton, England Dec. 22, 1969Jan. 4, 1972 Tecalemit (Engineering) Limited Jan. 3, 1969 Great Britainlnventor Appl. No. Filed Patented Assignee Priority CAM OPERATED FLUIDPUMPS 5 Claims, 4 Drawing Figs.

US. Cl

92/129 Int. Cl ..F04b 19/00, F04b 37/00 Field of Search 92/ 129;

[56] References Cited UNITED STATES PATENTS 2,819,678 1/1958 Nordell eta1 74/56 X 3,307,483 3/1967 Von Plato 417/471 3,314,594 4/1967 Rietdijk417/244 X 3,524,715 8/1970 Grantham 92/129 Primary ExaminerCarlton R.Croyle Assistant Examiner-R. E. Gluck Attorney-Mason, Kolehrnainen,Rathbum & Wyss ABSTRACT: This invention relates to a fluid pumpcomprising a piston which is reciprocable in a cylinder against abiasing force which may be a helical spring. The piston is caused toreciprocate in the cylinder by means of a cam system therein which maybe a ball rotated by a helical cam surface on one face of the piston.

PATENTEUJ N 41372 SHEET 2 BF 2 7 III/[III] VIII/1% CAM OPERATED FLUIDPUMPS This invention relates to cam operated reciprocating fluid pumpsfor use in a fluid system such as a lubricating system.

According to the invention a fluid pump comprises a cylinder havinginlet and outlet ports and a piston reciprocable within the cylinderagainst a biasing force by a helical cam system around the centerline ofthe piston and cooperating with a face thereof.

Preferably the face of the piston has a helical cam surface thereonwhich cooperates with a cam member rotatable relative to the helical camsurface. Desirably, the cam member is a ball between the helical camsurface on the piston and a ball support surface rotatable with respectto the piston.

A compact and convenient way of rotating the ball support surface withrespect to the piston is to journal this surface to a shaft which passesthrough the piston and is rotated by any suitable means such as anelectric motor. In order to retain the ball in its path, a shield may beprovided around the periphery of the ball support surface.

In a preferred construction, the biasing force for the piston is ahelical spring fitted around the upper region of the piston between anannular abutment thereon and a sleeve attached to the cylinder.

In order to keep friction losses in the pump to a minimum, the rotatableshaft carrying the ball support surface may be supported on a secondball disposed in a recess at the bottom of the cylinder. This ball islargely responsible for the very low-frictional characteristics andhigh-locational flexibility of the whole assembly. Further reductions infriction losses are also achieved by the rolling contact of the ball ofthe moving parts of the cam system.

According to a further feature of the invention, a passageway may beprovided connecting a second sealed cylinder to the main cylinder of thepump and this second cylinder has a piston reciprocable therein, thestroke of which can conveniently be altered by suitable means therebychanging the output capacity of the pump. This second piston may beconnected to means external of the pump which move with thereciprocating movement of the second piston. This feature serves auseful purpose in that when the pump is in operation, as the secondpiston moves in sympathy with the first piston, a visual indication,that the pump is in fact operating can readily be seen externally of thepump. This second piston also serves another useful purpose in that itcan be used to prime the main cylinder before the pump is set intooperation.

Each of the inlet and outlet ports may be closed by a oneway valve andit will be readily appreciated that the valve in the outlet port can beprovided externally of the pump. Further it will be appreciated that thedimensions of the pump can be selected so as to provide the pump withany desired output capacity.

The invention will now be described, by way of example, with referenceto the accompanying diagrammatic drawings, in which:

FIG. 1 is a cross section through a pump according to the invention;

FIG. 2 is a view of a section taken along the line IIII in FIG. 1;

FIG. 3 is a plan view of the pump of FIG. I, and

FIG. 4 illustrates a sight glass assembly incorporated in the pump.

Referring to the drawings there is shown a cyclic pump having a case 1and a lid structure 2 which houses an electric motor 3. The electricmotor is connected to a drive shaft 4 by means of a coupling 5. A driveplate 6 provided with a thrust face 7 is attached to the end of theshaft 4.

The drive shaft and drive plate fit into a cylinder 8 in a blockassembly 9, which assembly is disposed in the tank or reservoir portion10 of the pump. The cylinder 8 is increased in diameter at the endnearest the motor to receive a sleeve 11. A piston 12 is arranged aroundthe shaft 4 and in sliding engagement therewith, and is adapted to fitinto the cylinder 8, the piston having an annular abutment face 13 and asealing ring 14 of suitable material. The piston assembly is springbiased by means of a helical spring 15 fitted around the piston andabutting against face 13 of the piston and inner surface 16 of thesleeve 11.

The bottom of the piston is formed with a cam surface 28 and interposedbetween this cam surface and the drive plate is a ball 17.

The piston and cam surface are manufactured as a single unit and areconstrained to make a reciprocating motion only, thus rotation of thedrive plate 6 causes the ball 17 to roll between the cam and the thrustface 7, which results in a reciprocating motion of the piston. As thepiston is raised, the consequent depression induced in chamber 18results in fluid entering the cylinder through a spring biased inletvalve 19 (FIG. 2). On the return motion of the piston, the valve 19closes under the action of the spring and fluid is forced out of thepump through a nonreturn valve 20 in the outlet duct 41. In FIG. 1, theoutlet duct 41 which is formed in the block 9 is connected by a pipe 42to an outlet takeoff point 43 provided in the lid of the pump, thistakeoff point 43 having a union 44 so that the necessary pipe lines canbe connected thereto.

In addition to the cam-operated piston 12, there is provided anauxiliary second piston 21, which performs three functions. Firstly itmay be used as a priming attachment for the main pumping chamber 18,secondly it provides a visual check on whether the pump is operating ornot, and lastly it provides a means whereby the output of the pump canbe adjusted while remaining remote mechanically from the main operatingpiston.

In order to adjust the output of the pump, a hand knob 22, havingthreads 30 which cooperate with corresponding threads on the end of thepiston 21, can be rotated thereby raising or lowering the piston 21 in asecondary chamber 23 and thus varying the stroke of the auxiliarypiston. When the piston abuts against shoulder 24, the pump is set atmaximum output. According to the adjustment of the hand knob 22, thestroke of the auxiliary pump is restricted and will in its remainingstroke operate in sympathy hydraulically with the main piston via aninterconnecting passage 25. In the drawings, the stem of the piston 46is shown enclosed in a tube 45, the ends of which are fitted into theblock 9 and the casing lid respectively. This tube 45 can be omitted ifrequired providing a suitable fluid seal is provided between the pistonstem and the block.

The drive shaft 4 is located by means of the piston 12 which in turn islocated in the cylinder bore 8 over a short length of loosely fittingseal housing thereby allowing the drive plate end of the drive shaft tohave a large positional tolerance in relation to the drive end of theshaft adjacent the motor 3. This is, of course, a considerable advantagein manufacture.

A thrust point for the whole piston assembly is provided by a ball 26positioned in a recess 27 at the bottom of the cylinder 8. This ball islargely responsible for the very low-frictional frictionalcharacteristics and high-locational flexibility of the whole assembly.reduction in friction is also achieved by the rolling contact of ball 17between the cam surface 28 and the thrustface 7 of the drive plate.

A slight glass assembly 32 as shown in FIG. 4 can also be provided sothat a visual indication of the contents of the reservoir can beestablished during operation. The sight glass is fitted into anindentation 33 in one of the sidewalls of the case 1 and comprises aglass tube 34 having plugs 35 and 36 at each end fitted intocorresponding bores in the case and communicating with a breatherpassageway 37 and an inlet 38 respectively. When the reservoir in thetank is filled, the sight glass is also filled and drains simultaneouslywith the contents of the reservoir during operation to provide a visualindication of the contents of the reservoir at any time.

In operation, the tank 10 is filled with a fluid such as light ore andthe auxiliary piston 21 is pumped manually two or three times to primethe main pumping chamber 18. The electric motor is then put intooperation and consequently the drive shaft 4 is rotated. As the driveplate 6 is connected to this shaft, the drive plate is also rotated andcauses the ball 17 to roll along the cam surface 28. This movement ofthe ball on the cam surface forces the piston 12 upwardly against the action of the biasing spring 15 and draws a charge of fluid to be pumpedup through a filter element 29 and through the nonretum valve 19 intothe pumping chamber 18, the fluid also going into the secondary chamber23 through the passage 25.

When the ball comes off the cam surface, the spring 15 'forces thepiston downwardly thereby forcing the charge of fluid out of thechambers 18 and 23, and out of the pump through the outlet duct 41 viathe nonreturn valve 20. As the fluid is being pumped out, the secondarypiston is raised providing the external visual indication that the pumphas discharged its charge. At this stage the auxiliary piston is alsoforced downwardly by a spring 31 to the predetermined limit of itsstroke and the pump is then ready to begin the next cycle.

Since the auxiliary piston moves in synchronism with the main camoperated piston, the knob at the top of the pump can be seen toreciprocate up and down while the pump is in operation, therebyproviding a visual check as to the operation of the pump.

The pump described has a maximum capacity of 1 cc. since it has beendesigned for use in light industry for lubricating small machine tools,but the output of the pump can be varied by suitably modifying the boreof the cylinder or the length of the stroke.

I claim:

1. A fluid pump comprising a cylinder, a piston reciprocable in saidcylinder to provide a pump chamber, inlet and outlet ports in said pumpchamber, a spring biasing said piston in one direction, a cam systemconnected to the piston to reciprocate said piston, said cam systemcomprising, a first cam surface provided by a first end of said piston,a second cam surface, a drive member passing through said piston anddrivably connected to said second cam surface to rotate said second camsurface about the axis of the piston, mounting means for mounting saiddrive member adjacent said second cam surface, a ball disposed betweensaid cam surfaces to reciprocate said piston as the drive memberrotates.

2. A fluid pump as claimed in claim 1 in which the mounting meanscomprises a ball situated between said drive member and a recess in thebottom of said cylinder.

3. A fluid pump as claimed in claim 1 in which said first and second camsurfaces are situated in said pump chamber.

4. A fluid pump as claimed in claim 1 further comprising a passageway, asecond sealed cylinder, said passageway connecting said second sealedcylinder to said pump chamber, a second piston reciprocable in saidsecond sealed cylinder and means to vary the stroke of said secondpiston.

5. A fluid pump as claimed in claim 1 in which said second cam surfaceis flat and said first cam surface includes a drop ofi".

1. A fluid pump comprising a cylinder, a piston reciprocable in saidcylinder to provide a pump chamber, inlet and outlet ports in said pumpchamber, a spring biasing said piston in one direction, a cam systemconnected to the piston to reciprocate said piston, said cam systemcomprising, a first cam surface provided by a first end of said piston,a second cam surface, a drive member passing through said piston anddrivably connected to said second cam surface to rotate said second camsurface about the axis of the piston, mounting means for mounting saiddrive member adjacent said second cam surface, a ball disposed betweensaid cam surfaces to reciprocate said piston as the drive memberrotates.
 2. A fluid pump as claimed in claim 1 in which the mountingmeans comprises a ball situated between said drive member and a recessin the bottom of said cylinder.
 3. A fluid pump as claimed in claim 1 inwhich said first and second cam surfaces are situated in said pumpchamber.
 4. A fluid pump as claimed in claim 1 further comprising apassageway, a second sealed cylinder, said passageway connecting saidsecond sealed cylinder to said pump chamber, a second pistonreciprocable in said second sealed cylinder and means to vary the strokeof said second piston.
 5. A fluid pump as claimed in claim 1 in whichsAid second cam surface is flat and said first cam surface includes adrop off.